In Divided Christendom;: A Catholic study of the problem of reunion 
asks about the status of separated brothers, whether Orthodox or Protestant. He writes that if a child of Protestant parents is baptized in a way that “the form and intention of the rite are observed,” then “the child is thus truly incorporate in Christ and in the Church - the True Church. Traditional teaching here is clear and unanimous: children validly baptized in the separated Churches or dissident communities are genuinely members of the one true Church of Jesus Christ” (p. 230).
Though a baptized Protestant suffers because he is “in an objective Christian milieu which is impoverished and disordered,” yet the dissident’s adherence to “his sect or Church” though “objectively astray,” yet “leads straight to Christ and to true membership of His Church. He has the faith of Christ and truly belongs to His Church even though he has not the true faith and does not exteriorly belong to the true Church, He worships God truly, even if he does not worship him in truth . . . Such a dissident, even if he professes material heresy, cannot be called a heretic” (pp. 231-3). Though only God knows how many Protestant adhere to their dissidence in good faith such that they “have not lost the grace and infused faith of their baptism,” yet Catholics are free to believe that “the majority of dissidents are in completely good faith” (p. 234). A good Protestant is in a better condition than the indifferent Catholic; the first is on the way of salvation, the other “is heading for final loss” (p. 235).
Congar argues, however, that this reasoning does not extend to dissident communities:
Catholics “may , given certain conditions, have personal relations as one Christian with another with our separated brethren individually,” yet “we are not permitted to do so with the separated ‘Churches.’ As private individuals we may be indeed spiritually united to them in Christ, but there cannot be between them and us any ecclesiastical intercommunion” (p. 242). For this reason, “we cannot say that any dissident Christian body whatever is a member of the Una Ecclesia .” They have “elements” of Churchliness, “to the extent in which they have preserved in their very constitution as a religious body elements or principles which pertain to the integral reality of the One Church.” These elements are “realities whereby God gathers to Himself from the midst of mankind a People which He destines to be His heirs, and which He incorporates into His Christ,” specifically sacraments and the Word as interpreted through the apostolic order of the magisterium (pp. 242-3).
None of the dissident communities “preserved this ultimately reality by which the Church is constituted in unity,” and thus none can represent the Church. But the Orthodox are in Congar’s view in a better position than Protestants, for the latter have only baptism and marriage (as the “union of two validly baptized”) but “they have no other sacramental reality, no priesthood, ho teaching office in the strict sense of the word” (p. 243). Thus, not surprisingly, the terminus ad quem of Congar’s program of reunion is “Catholic unity; the unity, that is, of the fullness of the mystical Christ” that takes the form of “reintegration in the Una Catholica ” (p. 252).